1. Field of the Invention
The present invention generally relates to a projector, in particular, to an optical system.
2. Description of Related Art
In the recent years, projectors are widely utilised in various applications, such as meeting, education, and entertainment. Therefore, projectors with higher quality, smaller volume, lighter weight, and lower price are demanded.
Conventionally, a projector includes a projector lens and an optical system. FIG. 1A illustrates a conventional optical system. Referring to FIG. 1A, optical system 100 has a light source 110, a polarizing beam splitter (PBS) 120, and a light valve 130, an analyzer 140 and a lens 150. The PBS 120 disposed on the light path of the illumination beam L10 emitted by the light source 110, where the illumination beam L10 is separated into a first illumination beam L12 with S polarization and a second illumination beam with P polarization by the PBS 120. The first illumination beam L12 is reflected by the PBS 120, while the second illumination beam L14 passes through by the PBS 120. The first illumination beam L12 is then reflected by the light valve 130 and converted into an image beam L20 with P polarization. The image beam L20 passes through the PBS 120, the analyzer 140, and the lens 150.
FIG. 1B illustrates another conventional optical system. Referring to FIG. 1B, the difference between the optical system 100 in FIG. 1A and the optical system 100a in FIG. 1B is that the optical system 100a further includes a reflective polarizer 160 disposed between the light source 110 and the PBS 120. The reflective polarizer 160 transmits the first illumination beam L12 with S polarization, while reflects the second illumination beam L14 with P polarization. Thus, only the first illumination beam L12 reaches the PBS 120 and light valve 130 and being converted into image beam L20.